Current and continuing studies include correlation of T4 and T3 immunoassay results with metabolic and cardiovascular studies in nonthyroidal illness. Since we suspect that tissue delivery is related to the pattern of iodothyronine transport in serum, we hope to correlate the electrophoretically determined T4 and T3 distribution among serum proteins with the changing T4/T3 ratios in the sick patients. Total T4 and T3 secretion using turnover studies will also be carried out.